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opensimplex2d.go
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opensimplex2d.go
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package opensimplex2d
import "math"
type Noise interface {
Noise2D(x, y float64) float64
NormalizedNoise2D(x, y float64) float64
}
type noise struct {
perm []int16
}
func NewNoise(seed int64) Noise {
n := &noise{perm: make([]int16, 256)}
var source [256]int16
for i := range source {
source[i] = int16(i)
}
seed = seed*6364136223846793005 + 1442695040888963407
seed = seed*6364136223846793005 + 1442695040888963407
seed = seed*6364136223846793005 + 1442695040888963407
var i int32
for i = 255; i >= 0; i-- {
seed = seed*6364136223846793005 + 1442695040888963407
r := int32((seed + 31) % int64(i+1))
if r < 0 {
r += i + 1
}
n.perm[i] = source[r]
source[r] = source[i]
}
return n
}
func (n *noise) Noise2D(x, y float64) float64 {
var noisyValue float64
stretchOffset := (x + y) * StretchConstant2
xs := x + stretchOffset
ys := y + stretchOffset
xsb := math.Floor(xs)
ysb := math.Floor(ys)
squishOffset := (xsb + ysb) * SquishConstant2
xb := xsb + squishOffset
yb := ysb + squishOffset
xins := xs - xsb
yins := ys - ysb
inSum := xins + yins
dx0 := x - xb
dy0 := y - yb
var value float64 = 0.0
dx1 := dx0 - 1 - SquishConstant2
dy1 := dy0 - 0 - SquishConstant2
attn1 := 2 - dx1*dx1 - dy1*dy1
if attn1 > 0 {
attn1 *= attn1
value += attn1 * attn1 * extrapolate2(n.perm[:], xsb+1, ysb+0, dx1, dy1)
}
dx2 := dx0 - 0 - SquishConstant2
dy2 := dy0 - 1 - SquishConstant2
attn2 := 2 - dx2*dx2 - dy2*dy2
if attn2 > 0 {
attn2 *= attn2
value += attn2 * attn2 * extrapolate2(n.perm[:], xsb+0, ysb+1, dx2, dy2)
}
var xsvExt, ysvExt, dxExt, dyExt float64
if inSum <= 1 {
zins := 1 - inSum
if zins > xins || zins > yins {
if xins > yins {
xsvExt = xsb + 1
ysvExt = ysb - 1
dxExt = dx0 - 1
dyExt = dy0 + 1
} else {
xsvExt = xsb - 1
ysvExt = ysb + 1
dxExt = dx0 + 1
dyExt = dy0 - 1
}
} else {
xsvExt = xb + 1
ysvExt = ysb + 1
dxExt = dx0 - 1 - 2*SquishConstant2
dyExt = dy0 - 1 - 2*SquishConstant2
}
} else {
zins := 2 - inSum
if zins < xins || zins < yins {
if xins > yins {
xsvExt = xsb + 2
ysvExt = ysb + 0
dxExt = dx0 - 2 - 2*SquishConstant2
dyExt = dy0 + 0 - 2*SquishConstant2
} else {
xsvExt = xsb + 0
ysvExt = ysb + 2
dxExt = dx0 + 0 - 2*SquishConstant2
dyExt = dy0 - 2 - 2*SquishConstant2
}
} else {
xsvExt = xsb
ysvExt = ysb
dxExt = dx0
dyExt = dy0
}
xsb += 1
ysb += 1
dx0 = dx0 - 1 - 2*SquishConstant2
dy0 = dy0 - 1 - 2*SquishConstant2
}
attn0 := 2 - dx0*dx0 - dy0*dy0
if attn0 > 0 {
attn0 *= attn0
value += attn0 * attn0 * extrapolate2(n.perm[:], xsb, ysb, dx0, dy0)
}
attnExt := 2 - dxExt*dxExt - dyExt*dyExt
if attnExt > 0 {
attnExt *= attnExt
value += attnExt * attnExt * extrapolate2(n.perm[:], xsvExt, ysvExt, dxExt, dyExt)
}
noisyValue = value / NormConstant2
return noisyValue
}
func (n *noise) NormalizedNoise2D(x, y float64) float64 {
noisy := n.Noise2D(x, y)
normalizedNoisy := (noisy + NormMinConstant2) / (2.0 * NormMinConstant2)
return clamp(normalizedNoisy, 0.0, 1.0)
}
func extrapolate2(perm []int16, xsb, ysb, dx, dy float64) float64 {
index := perm[(int32(perm[int32(xsb)&0xff])+int32(ysb))&0xff] & 0x0e
g1 := float64(Gradients2[index])
g2 := float64(Gradients2[index+1])
return g1*dx + g2*dy
}
func clamp(x, min, max float64) float64 {
if x > max {
return max
}
if x < min {
return min
}
return x
}